Vehicle detection technology is focusing on detecting and acquiring traffic information about the vehicles on the road, and the main information includes: the traffic volume, the direction, the speed of the vehicles, the location and the type of vehicle. At present, the induction coil is used in the widespread detection method about vehicle detection technology, which is commonly known as a “ground inductance coil”. The circular induction coil is embedded in the subsurface of the roads, and the circular induction coil generates a magnetic field when it is energized. While there is a vehicle passing, which cutting through the magnetic field generated by the circular induction coil, so that causing the changes in electromagnetic induction and then implementing the detection of the presence of the vehicles.
The China Patent by Gu (CN 2258299Y) discloses a vehicle detection device, including an outer annular coil which is shallowly buried under the road surface and served as a sensor coil, a vehicle detection device body, a vehicle detection circuit, as well as transmission cables which connecting the vehicle detection circuit and outer annular coil. An oscillator, which is connected to the outer annular coil, wherein one of its output terminals is connected to a voltage comparator and another terminal is connected to a first driver. The voltage comparator transfer the oscillator signal into the pulse signal, and oscillation frequency is calculated by the trigger, the counter and the micro computer. This patent provides corresponding anti-interference means against various environment interferences to avoid the dead lock. However, this type of vehicle detection device disadvantaged in:
1. Long construction duration and traffic affect because of blocking the road.
2. Destroying the surface of the road and impact the appearance of the road.
3. The high rate of damage, which is caused by the coil fracture due to the road oscillation.
4. Difficulty in maintenance, including the difficulty in finding the damaged point and long construction duration of the maintenance.
The SHIMIZU's patent (U.S. Pub. No. US2009/0278710A1) discloses a moving vehicle system and method of detecting position of moving vehicle, a detection head has an array including a plurality of coils. Magnetic marks are arranged in a travel route at a pitch equal to the array length. By interaction between the magnetic marks and the coils, a position of a moving vehicle is determined based on the magnetic marks.
The Lohberg's patent (US 2004/0100251A1) discloses active magnetic field sensor, use thereof, method and device, The present invention relates to an active magnetic field sensor, in particular a wheel bearing sensor unit, comprising at least one magnetic sensor element for converting a temporally periodic magnetic field into a temporally periodic electric sensor signal at signal outputs and an electronic signal-evaluating circuit, the said magnetic field sensor being electrically fed by way of a sensor interface, wherein an active electric processing of periodic signals of the magnetic sensor element is performed in two or more separate signal channels of the evaluating circuit respectively associated with the sensor signals. The present invention further discloses a motor vehicle influencing device and a method preventing a vehicle from rolling on an inclined plane.
Therefore, although there are many vehicle detection devices used for detecting traffic situation, such as the above disclosed, the installation of the vehicle detections are still difficult, and the construction duration is long, and it needs to destroy the roads and affecting the surface appearance. Further more, the coil which is used in most vehicle detection devices is easy to be destroyed because of the road vibration, and it is difficult to find where the broken point is, and it costs a long time to repair as well.